90 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



transition substance. From the similarities, dissimilarities, and transitions which exist 

 between starch and cellulose, he believes that starch and cellulose are not homogeneous 

 substances, but compound bodies having a common organic element. 



Reinsch (Neue Jahrbiicher f. Pharm., 1855, iii, 65) records that potato starch contains 

 dextrin and sugar which are set free in water when the grains are pulverized. Nageli 

 (Tageblatt d. 32, Versaminlung deutscher Naturforscher u. Aerzte in Wein, 1856) found 

 that a substance giving a blue reaction with iodine could be derived from starch without 

 changing the structure. This work is reviewed in his elaborate monograph which was 

 published in 1858 {loc. cit.). Payr (Jour. f. prakt. Chemie, 1856, lxix, 425) studied the 

 action of cliloride of zinc on the starch of the horse chestnut. He noted that the grains 

 are dissolved, leaving a very small residue. He made preparations in the cold and at 

 100°, which were filtered, precipitated with alcohol, and dried. From both he obtained 

 a carbohydrate in combination with zinc, but the preparation made at high temperature 

 contained only a twelfth part of the zinc salt that was contained in former. He deter- 

 mined the elementary composition, and concluded that the carbohydrate separated is 

 not starch, because it dissolves easily in water and does not give a blue reaction -nith 

 iodine; nor could it be dextrin or sugar, he concludes, yet it goes easily into sugar on warm- 

 ing with dilute acid. 



In 1857 Wolff (Jour. f. prakt. Chemie, 1857, lxxi, 91) examined the proportions of 

 water and the ash constituents of a number of starches. Melsens (Institut, 1857, xxv, 

 161; quoted by W. Nageli, loc. cit.) found that the starch-grains when treated with dilute 

 acids, pepsin, or diastase may be so altered in composition, without changing their form, 

 that they then no longer stain blue with iodine. During the same year Fresenius (Ann. 

 d. Chem. u. Pharm., 1857, 102, 184) reported his observations that as the temperatiu"e 

 was lower the intensity of the color reaction of the starch solution to iodine was greater. 



Mulder (Chemie des Bieres, Leipzig, 1858, 166) found, after subjecting starch to extract 

 of malt, dilute sulphuric acid, and roasting, respectively, that the dextrins formed differ from 

 each other, as was shown by their behavior in relation to certain precipitants. 



In 1858 Carl Nageli published his elaborate monograph (Die Starkekorner, etc., 

 loc. cit.), from which quotations have been made in the preceding chapter, and which will 

 be referred to in subsequent pages. Von Mohl (Botanische Zeitung, 1859, xvii, 225) 

 took exception to the statement of Nageli that when starch-grains are subjected to the 

 action of saliva the granulose is dissolved out wliile the cellulose remains, and that the 

 reaction of starch and cellulose with iodine furnish a means of differentiation, etc. (See 

 Chapter II, page 27.) 



Payen (Compt. rend., 1859, xlviii, 67) found that the reaction of starch and cellulose 

 with iodine is almost the same, but that it differs under the influence of diastase, and also 

 towards an ammoniacal solution of copper oxide, cellulose beuig soluble in the latter, 

 but not so with amylose. Niepce de Saint-Victor and Convisart (Compt. rend., 1859, 

 XLix, 368) ascertained that sugar and dextrin are formed from starch-paste that had been 

 subjected to the action of the sun. Wicke (Ann. d. Physik. u. Chemie, 1859, cviii, 359) 

 states that pulverized starch-granules do not dissolve in water, but this statement is in con- 

 tradiction to the records of many previous observers and is fully disproved by the inves- 

 tigations of Jessen (Ann. d. Phys. u. Chemie, 1859, cvi, 497; 1860, cix, 361), and later 

 experimenters. Jessen writes that one can easily convince himself of the solubility of 

 raw starch by crushing the starch-grains in a little water, when the beginning of solution 

 is at once noted, the entire mass becoming viscous and mucilaginous. On the addition 

 of more water a clear solution is obtained on whose surface float torn and broken coats 

 of the starch-grains, while the unbroken grains sink to the bottom. The filtered liquid 

 became blue on the addition of iodine, and the iodine-starch is, he states, contrary to 

 C. Niigeli's statement, completely soluble in pure water. 



